Add architecture for simulating memory pressure notifications in all processes

content/common/memory_messages.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file contains IPC messages for controlling memory pressure handling
 // in child processes for the purposes of enforcing consistent conditions
 // across memory measurements.
 
 // Multiply-included message header, no traditional include guard.
 
+#include "base/memory/memory_pressure_listener.h"
 #include "ipc/ipc_message_macros.h"
 #include "content/common/content_export.h"
 
 #undef IPC_MESSAGE_EXPORT
 #define IPC_MESSAGE_EXPORT CONTENT_EXPORT
 
 #define IPC_MESSAGE_START MemoryMsgStart
 
-// Sent to all child processes to enable/disable suppressing memory
+using MemoryPressureLevel = base::MemoryPressureListener::MemoryPressureLevel;
+
+IPC_ENUM_TRAITS_VALIDATE(
+    MemoryPressureLevel,
+    (value == MemoryPressureLevel::MEMORY_PRESSURE_LEVEL_MODERATE ||
+     value == MemoryPressureLevel::MEMORY_PRESSURE_LEVEL_CRITICAL))
+
+// Sent to all child processes to enable/disable suppressing memory pressure
 // notifications.
 IPC_MESSAGE_CONTROL1(MemoryMsg_SetPressureNotificationsSuppressed,
                      bool /* suppressed */)
+
+// Sent to all child processes to simulate a memory pressure notification.
+IPC_MESSAGE_CONTROL1(MemoryMsg_SimulatePressureNotification,
+                     MemoryPressureLevel /* level */)